This invention relates to operational amplifiers and more particularly to an operational amplifier operated as a unity gain amplifier for sourcing current to capacitive loads.
Generally, unity gain or voltage follower amplifiers comprising operational amplifiers are known in the art. For example, a typical operational amplifier has positive and negative inputs and an output and can be operated in a unity gain mode by providing feedback between the output and the negative input. Moreover, operational amplifiers are generally available for both sinking and sourcing current to a load. However, typical operational amplifiers cannot source current to large capacitive loads.
Operational amplifiers available today include an emitter-follower output stage for either sourcing or sinking current to a load. Additionally, these operational amplifiers include internal capacitors for providing phase compensation to ensure stability if negative feedback is used. Therefore, if these operational amplifiers are used to drive a large capacitive load instability problems may very well occur. These instability problems arise from the fact that the large capacitive load creates a second "pole" in the transfer function of the circuit which can create an instability problem which causes oscillation.
In view of the above, it is quite apparent that typical operation amplifiers may not be useful for driving large capacitive loads. Therefore, a need exists to provide an operational amplifier which can be utilized for sourcing current only to capacitive loads.